Microbiology- Antibiotic Therapy Flashcards
Selective toxicity
Minimal toxicity to host ie closely targets bacteria
Bactericidial
kills bacteria
Bacteriostatic
inhibits bacterial growth
Ideal antibiotic
selective toxicity cidal long half life good tissue distribution lack of side effects oral and parenteral preparation
Pros of penicillins
- Safe
- flexible molecule
narrow to broad spectrum - excreted rapidly by kidneys
- safe in pregnancy
Cons of penicillins
- Patients can be hypersensitive
- rapid excretion means frequent dosing
- resistance
Common cell wall antimicrobials
Penicillins, cephalosporins, glycopeptid3s
Target of beta lactams
Penecillin Binding Proteins
Penicillin active against Gm +ve organisms
Flucloxacillin (IV, oral)
Penicillin active against Gm +ve and -ve organisms
Amoxicillin and co-amoxiclav (both IV, oral)
Penicillin active against Gm -ve organisms
Temocillin (IV only)
Three principle compounds of penicillin
Benzylpenicillin, phenoxymethyl penicillin, benzathine penicillin
Co-amoxiclav
Beta lactam and beta lactamase inhibitor
Flucloxacillin spectrum
Very narrow spectrum antibiotic
Staphylococci and streptococci only
Which type of organisms is temocillin active against?
Extended spectrum β-lactamases producing organisms
What is Temocillin resistant to?
B lactamase resistant
How do cephalosporins work?
they inhibit cell wall synthesis and are bactericidal
Why are cephalosporins avoided in hospitals?
they have a broad spectrum and kill off normal gut flora, allowing for C. Diff overgrowth. this can lead to gastroenteritis
Examples of Glycopeptides
Vancomycin, Teicoplanin
Which type of bacteria do glycopeptides target?
ones with a gram positive cell wall
How do antibiotics inhibit protein synthesis?
they attach to bacterial ribosomes (different from mammalian ribosomes)
The only antibiotic which is bactericidal and targets protein synthesis
Aminoglycosides eg gentamicin- irreversibly binds to 30s ribosomes irreversible
4 antibiotics to avoid, due to increased risk of C. Diff
Cephalosporins
Co-amoxiclav
Ciprofloxacin
Clindamycin
Examples of bacteriostatic antibiotics
Tetracyclines
Macrolides (eg erythromycin, clarythromycin)
How are macrocodes excreted?
via the liver, biliary tract and into the gut
Which antibiotics affect nucleic acids?
Metronidazole
Trimethoprim
Fluoquinolones
What organisms is metronidazole active against?
Anaerobes (and protozoa)
Which antibiotic is commonly given for acute UTIs?
Trimethoprim
